Why firebase recyclerview is not working correctly?

Question

I try to open each video when I click on them but what I get instead is only the second video (sometimes first video). For example, when I click on "16 best video ideas for small business" I want it to open that particular video. But what I get instead is "this tiny camera can show the world from a bug's point of view. I think the problem occurs because of for loop inside query in UserHomeVideoAdapter.

UserHomeVideoAdapter.java:

public class UserHomeVideoAdapter extends FirestoreRecyclerAdapter<FollowList, UserHomeVideoAdapter.UserVideoHolder> {

Context context;
final FirebaseFirestore db = FirebaseFirestore.getInstance();

String thumbUrl, videoTitle, videoUrl, videoDesc, videoId, publisherId;

Video video;

public UserHomeVideoAdapter(@NonNull @NotNull FirestoreRecyclerOptions<FollowList> options, Context context) {
    super(options);
    this.context = context;
}

@Override
protected void onBindViewHolder(@NonNull @NotNull UserVideoHolder holder, int position, @NonNull @NotNull FollowList model) {

    Query query = db.collection("Videos").whereEqualTo("publisherId", model.getUserId());

    query.get().addOnCompleteListener(task -> {
        if (task.isSuccessful()) {
            if (task.getResult() != null) {
                for (QueryDocumentSnapshot documentSnapshot : task.getResult()) {
                    video = documentSnapshot.toObject(Video.class);

                    Log.d("Data", documentSnapshot.getId() + " => " + documentSnapshot.getData());

                    thumbUrl = video.getThumbUrl();
                    videoTitle = video.getVideoTitle();
                    videoUrl = video.getVideoUrl();
                    videoDesc = video.getVideoDesc();
                    videoId = video.getVideoId();
                    publisherId = video.getPublisherId();
                }

                if (task.getResult().size() != 0) {
                    Glide.with(context).load(model.getUserImageUrl()).into(holder.userProfileImage);
                    Glide.with(context).load(thumbUrl).into(holder.videoImageView);
                    holder.videoTitle.setText(videoTitle);
                    holder.mainContainerVideo.setVisibility(View.VISIBLE);
                } else if (task.getResult().size() == 0) {
                    holder.mainContainerVideo.getLayoutParams().height = 0;
                    holder.mainContainerVideo.getLayoutParams().width = 0;
                }
            }
        } else {
            Toast.makeText(context, String.valueOf(task.getException()), Toast.LENGTH_SHORT).show();
        }
    }).addOnFailureListener(e -> Toast.makeText(context, e.getLocalizedMessage(), Toast.LENGTH_SHORT).show());

    holder.videoContainer.setOnClickListener(v -> {
        Intent intent = new Intent(context, VideoActivity.class);
        intent.putExtra("videoPublisherUserName", model.getUserName());
        intent.putExtra("thumbUrl", thumbUrl);
        intent.putExtra("videoPublisherEmail", model.getUserEmail());
        intent.putExtra("videoUrl", videoUrl);
        intent.putExtra("videoId", videoId);
        intent.putExtra("videoPublisherFullName", model.getUserFullName());
        intent.putExtra("videoPublisherId", publisherId);
        context.startActivity(intent);
    });

}

@NonNull
@NotNull
@Override
public UserVideoHolder onCreateViewHolder(@NonNull @NotNull ViewGroup parent, int viewType) {
    View v = LayoutInflater.from(context).inflate(R.layout.video_cell, parent, false);
    return new UserVideoHolder(v);
}

public static class UserVideoHolder extends RecyclerView.ViewHolder {
    RelativeLayout videoContainer, mainContainerVideo;
    CircleImageView userProfileImage;
    TextView videoTitle;
    ImageView videoImageView;

    public UserVideoHolder(@NonNull @NotNull View itemView) {
        super(itemView);
        mainContainerVideo = itemView.findViewById(R.id.mainContainerVideo);
        videoContainer = itemView.findViewById(R.id.videoContainer);
        userProfileImage = itemView.findViewById(R.id.userProfileImage);
        videoTitle = itemView.findViewById(R.id.videoTitle);
        videoImageView = itemView.findViewById(R.id.videoImageView);
    }
}
}

I logged videoId inside that is assigned inside for loop. Sometimes it returns ids in this order "1"; "2" and sometimes it returns like this "2"; "1". When it returns in this order "1"; "2" click opens second video even if I click first video and when it returns like this "2"; "1" click opens first video even if I click second video.

If you need additional code to solve the problem please ask and I will provide it as soon as possible. Any help is appreciated. Thanks

Answer 1

The short answer is that onBindViewHolder() is trying to do too much. From the documentation :

Called by RecyclerView to display the data at the specified position. This method should update the contents of the ViewHolder#itemView to reflect the item at the given position.

In other words, onBindViewHolder() is only responsible for one single item in the RecyclerView . However, you are trying to fetch all of the data for every element in the list. Instead, you should fetch the data external to your adapter and pass it in as a parameter. Then onBindViewHolder() should update the UI elements of a view inside the RecyclerView to display whatever you want for one single item.

Google has a great example CustomerAdapter . First, the constructor takes the list of data that will be displayed:

    public CustomAdapter(String[] dataSet) {
        mDataSet = dataSet;
    }

Then onbindViewHolder() is only responsible for setting what is displayed in the UI of a single item in the RecyclerView:

    @Override
    public void onBindViewHolder(ViewHolder viewHolder, final int position) {
        Log.d(TAG, "Element " + position + " set.");

        // Get element from your dataset at this position and replace the contents of the view
        // with that element
        viewHolder.getTextView().setText(mDataSet[position]);
    }

It does NOT try to get data or loop over a list or anything else. All of that is someone else's responsibility.